Figure 112a

Atrial Septal Defect with Resultant Left-to-Right Shunting.
Blood from the pulmonary veins enters the left atrium, after which some of it crosses the atrial septal defect into the right atrium and ventricle (longer arrow).

Reference Brickner, M.E., Hillis, L.D., and Lange, R.A., Medical Progress: Congenital Heart Disease in Adults (first of two parts), The New England Journal of Medicine, p 256-263